1. Field of the Invention
The present invention relates to a suspension device in which a knuckle is supported by an upper arm and a lower arm. More particularly, the present invention relates to a suspension device in which a knuckle is formed by connecting a knuckle body forged or cast from light alloy and a lower arm support bracket made of ferrous metal, and a suspension device in which an outer end of a lower arm in a vehicle width direction is supported on a lower arm support bracket connected to a lower surface of an upper arm body via a ball joint.
2. Description of the Related Art
FIG. 5 shows a knuckle 01 of a suspension device according to a first conventional example (Prior Art 1). The knuckle 01 is formed by connecting a lower arm support bracket 03 made of ferrous metal to a lower end of a knuckle body 02 forged from light alloy with two bolts 04 and 05, an outer end of an upper arm 06 in a vehicle width direction is connected to an upper end of the knuckle 01, and an outer end of a lower arm 07 in the vehicle width direction is connected to the lower arm support bracket 03. A pair of bosses 02a and 02b protruding downward are integrally formed at front and rear ends in a lower portion of the knuckle body 02 to which the lower arm 07 is connected. Front and rear ends of the lower arm support bracket 03 are fastened to lower surfaces of the bosses 02a and 02b with the bolts 04 and 05.
FIG. 6 shows a knuckle 01 of a suspension device according to a second conventional example (Prior Art 2). A space 08 is formed between a recess 02c interposed between a pair of bosses 02a and 02b of a knuckle body 02 and an upper surface of a lower arm support bracket 03, and an outer end of a lower arm 07 in a vehicle width direction is secured with a nut 09 to an upper end of a ball joint 010 oscillably supported on the lower arm support bracket 03 and extending into the space 08.
In the knuckle 01 of the suspension device according to Prior Art 1, the pair of bosses 02a and 02b significantly protrude from the lower portion of the knuckle body 02, thus the elongated bosses 02a and 02b may cause degradation in forgeability to increase manufacturing costs, and strength of the bosses 02a and 02b may be insufficient to which a heavy load from the lower arm 07 is transferred. Also when the knuckle body 02 is cast from light alloy, the elongated bosses 02a and 02b may interfere with flowing molten metal to cause degradation in castability, and cavities may be created in the bosses 02a and 02b to reduce quality.
In the knuckle 01 of the suspension device according to Prior Art 2, when the nut 09 loosens from vibration caused by driving of a vehicle, the lower arm 07 may fall off from the ball joint 010 leading to separation of the lower arm 07 from the knuckle 01.